Your first problem will be that once the grass/weeds are removed from this slope you have opened it up to erosion. So it would be best to terrace across the slope with railroad ties or rocks to stabilize it. Then plant ten beach plum bushes (Prunus maritima) on the slope underplanted with either Bar Harbor juniper (Juniperous horizontalis 'Bar Harbor') or Shore juniper (Juniperous conferta) which will remain low growing and in time cover the slope. This will give you all year green plus decidous shrubs which bloom in the spring and bear a fruiting crop for jelly and pies. All three plant types will grow well in the adverse situation you describe.

Great, thanks! The junipers will be very slow to spread, no? At least the ones I have on the southeast side of the house have barely grown in the past two years.

Very helpful. Thanks again.